81646237940 has 24 divisors (see below), whose sum is σ = 173383587720. Its totient is φ = 32291545088.

The previous prime is 81646237903. The next prime is 81646237951. The reversal of 81646237940 is 4973264618.

It can be written as a sum of positive squares in 4 ways, for example, as 5618102116 + 76028135824 = 74954^2 + 275732^2 .

It is a super-2 number, since 2×81646237940² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22932557 + ... + 22936116.

It is an arithmetic number, because the mean of its divisors is an integer number (7224316155).

Almost surely, 2^81646237940 is an apocalyptic number.

It is an amenable number.

81646237940 is an abundant number, since it is smaller than the sum of its proper divisors (91737349780).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81646237940 is a wasteful number, since it uses less digits than its factorization.

81646237940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45868771 (or 45868769 counting only the distinct ones).

The product of its (nonzero) digits is 1741824, while the sum is 50.

The spelling of 81646237940 in words is "eighty-one billion, six hundred forty-six million, two hundred thirty-seven thousand, nine hundred forty".